JPH01110248A - Defect monitor for inner surface of piping - Google Patents

Abstract

PURPOSE:To estimate the shape of a cracking easily, by a method wherein a plurality of probes for measuring a potential difference are provided at inspecting points on a surface at a specified internal and a potential on the surface of a piping is measured in a time sharing manner to calculate a potential distribution pattern near the points. CONSTITUTION:A constant current source unit 7 is connected being mounted over a part 6 to be inspected of a piping 5 while multiple-point probes 1 are disposed on the surface thereof. Signals of the probes 1 are applied to a multiple point potential difference measuring memory 2 to measure potentials of the probe 1 in a time sharing manner and the results are stored together with the position thereof. A cracking identifier 3 in which a potential distribution is numerically analyzed beforehand when the piping 5 has a defect receives an input of information from the multiple point potential difference measuring memory 2 to estimate geometric dimensions of a cracking [depth (a), length 2c and the like] by computation and the results are stored. A safety analyzer 4 previously receives an input of information such as a time-series change in the temperature T and pressure P of metal of a piping, a relationship among quality of material and temperature and a destruction dynamic parameter and material and dimensional specifications of the piping and computes a destruction dynamic parameter based upon the information from the cracking identifier 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a defect monitoring device for the inner surface of piping, which is applied to various types of piping such as atomic couplants, boilers, turbines, and chemical plants.

[Conventional technology]

Conventionally, to detect defects (cracks or thinning) on the inner surface of a pipe, ultrasonic flaw detection is performed on the target position from the outer surface, or a probe is inserted into the inner surface of the pipe and ultrasonic flaw detection is performed on the inner surface. Five methods have been used to perform magnetic particle or liquid penetrant testing directly on defects.

Furthermore, estimating the shape of a forging by potential difference is performed in order to estimate the three-dimensional defect shape by arranging a probe to straddle the crack on the surface where the crack exists. It has been used as a row 5 method since its existence was known.

[Problem that the invention seeks to solve]

The above conventional method has the following problems.

(1) Among the conventional methods, ultrasonic flaw detection is a method that detects the presence or absence of defects by exploring the entire target area with a contactor, and is used at high temperatures and
It cannot be used for constant monitoring of piping operating at high pressure.

(2) Defect detection using magnetic powder or liquid penetrant testing is effective only when the defective area on the inner surface of the pipe can be directly observed and cannot be used while the pipe is in operation.

(3) The conventional method of defect detection using electrical resistance or potentiometric method is to know that a crack exists on the surface where the crack is open, and then attach probes to two points that sandwich the crack. This is a method for estimating the three-dimensional manufactured shape by measuring these electrical resistances and potential differences. This method relies on recognizing the presence of cracks, and cannot constantly monitor defects on the inner surface of the pipe that occur at unspecified locations from the outside.

[Means for solving problems]

The present invention takes the following measures to solve the above problems.

That is, a plurality of potential difference measurement probes arranged at predetermined intervals on the surface of the piping inspection point, a multi-point potential difference measurement storage device that inputs the outputs of the same plurality of potential difference measurement probes, and a multi-point potential difference measurement storage device that inputs the outputs of the same plurality of potential difference measurement probes; A crack identification device that inputs the output of the potential difference measurement storage device and a safety analysis device that inputs the output of the crack identification device are provided.

[Function] By the above means, the potential on the surface of the pipe is measured and calculated in time series. When a crack occurs on the inner surface of the pipe, the potential at that part changes, so the potential distribution pattern in the vicinity is calculated. The shape of the crack can be estimated from this potential distribution nozzle turn.

Next, fracture mechanics parameters are calculated, and unstable fracture evaluation and crack propagation are subjected to speed evaluation calculations and output. In this way, cracks on the inner surface of the high-temperature, high-pressure pipe that occur during operation can be immediately detected by surface measurement, and unstable fracture evaluation and crack propagation speed can be easily evaluated.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 to 4. As shown in Fig. 1, the piping 5.5' is arranged to be tested, the output of the probe 1 is input to the multi-point potential difference measurement storage device 2, and the output of the multi-point potential difference measurement storage device 2 is used for crack identification. Furthermore, the output of the crack identification device 3 is input to the safety analysis device 4.

In the above configuration, 1. Normally, high temperature/high pressure piping 5, 5
Since the defect occurrence area of ' is mostly the weld lines 6 and 6', the inspected parts are mainly the weld lines 6 and 6 as shown in Fig.
Take a narrow region between ′.

Multiple point probes 1 installed at predetermined intervals in this area
The multi-point potential difference measurement/memory device 2 receives the signal, measures the potential of each probe 1 in time series, and stores it together with its position. The concept is shown in FIG. 1(a). Note that each potential is measured at two points, for example, as shown in FIG. 2, each probe P(i, j) of a multi-point probe 1 (1=1 to 4 in FIG. 2).
'(A') for the potential difference Δ between the positions indicated by the arrows of
, m) (1=o~3゜m=1~6) are measured in a predetermined sequence and processed to calculate the time series potential Δ)i: (t, x, y) after the initial value of each probe point. required (first
Figure (a)).

For example, if the current source device 7 is connected as shown in FIG. 3(a), the potential in the Y direction of each probe point at time t□ is determined when there is no defect d.

A dotted line a in FIG. 3(1)) is obtained. If there is a defect d, a solid line in the figure is obtained.

If a defect occurs on the inner surface of the pipes 5, 5', the potential will change, so the position of each probe (J, m
) at that time (1) is calculated.

Δv(t, zsm) = ΔE(t, zsm) − ΔE(o
J, m) ... (1) Change in potential Δv (t, zsm)
exceeds a predetermined value, the nearby position (x, y
) is calculated and stored. The concept is shown in FIG. 1(b).

The crack identification device 3 detects defects (
Information obtained by numerical analysis (the analysis method is the boundary element method, finite element method, etc.) of the potential distribution when there are various shapes) is input in advance. By inputting the reference function of the relationship between the potential ΔE and the position, the information on the defect shape, and the information from the multi-point potential difference measurement storage device 2, and using the information from the operator, as shown in FIG. 4(a), The potential change Δv(ts'', y) at each coordinate position (X, 7) is calculated and output.

If there is a defect d, this output will be as shown in FIG. 4(b). For comparison, FIG. 6(c) shows a case with no defects. Furthermore, this output and the former information, that is, the potential Δ
A reference function of the relationship between E and position (x, y) and information on the defect shape are calculated and compared, and the dimensions of the forged shape (depth a.

(length 20, etc.) is estimated and stored. on the other hand.

The rate of change of cracks is estimated and calculated from this past information in time series.

The safety analysis device 4 uses the time-series changes in the temperature (T) and pressure (P) of the metal of the pipes 5, 5', the material, and the information from the temperature crack identification device 3 to express the equation (2) in advance. The fracture mechanics parameter K or J is calculated and output in time series.

K (or J) = f (P, a, a/2c, a/l)
-・-・-(2) However, a: Crack depth 2C: Crack length t: Pipe wall thickness In addition, calculations for unstable fracture evaluation and crack propagation speed evaluation are performed as follows. That is, the fracture mechanics parameter K or J, which changes hourly, is compared with a predetermined value that has been input in advance, and when it exceeds the predetermined value, an alarm display is output.

In this way, the occurrence of cracks on the inner surface of high-temperature, high-pressure piping can be easily detected, and unstable fracture evaluation and crack propagation speed can be evaluated.

〔Effect of the invention〕

The present invention has the following effects.

(1) Monitoring of aging deterioration of various plant piping, including nuclear couplants, is becoming very important.

According to the present invention, safety can be continuously monitored and accidents can be prevented.

(2) Defects on the inner surface of piping that occur at unspecified locations.

Can be constantly monitored from the outside while the piping is in operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the arrangement of probes and the potential difference measuring section of the same embodiment, and FIG.
The figure is an explanatory diagram of the potential distribution along the Y direction of the same example. Figure (a) is a diagram showing the relationship between the probe arrangement and defect position, etc., and Figure (b) is a potential distribution diagram corresponding to (a). , Figure 4 is an explanatory diagram of the electric potential distribution in the x and y planes of the same example. Figure (a) is a diagram showing the relationship between the probe arrangement and defect position, and Figure 4 (b) is a diagram of the potential when there is a defect. A distribution diagram of changes. FIG. 3(C) is a distribution diagram of changes in potential in the case of no defects. In the figure: 1: Multi-point potential difference measurement probe (fixed by welding to the outer surface of the pipe) 2: Multi-point potential difference measurement storage device 3: Crack identification device 4: Safety analysis device 5.5':
Piping body 6, 6': Welding line 7: Constant current source device
a: If there is a defect b: If there is no major defect d: Defect

Claims (1)

[Claims] a plurality of potential difference measurement probes arranged at predetermined intervals on the surface of a piping inspection location; a multi-point potential difference measurement storage device into which the outputs of the plurality of potential difference measurement probes are input;
A defect monitoring device for an inner surface of a pipe, comprising: a crack identification device that inputs the output of the multi-point potential difference measurement and storage device; and a safety analysis device that inputs the output of the crack identification device.